1. Field of the Invention
The general field of the invention relates to a unique multiple input switch design, particularly suitable for electromagnetic radiation applications, such as multiple antenna or multiple radiation beam applications.
2. Related Arts
Various antenna arrangements require switching among multiple antennas to a single or multiple reception circuitries. For example, some antennas may have multiple selectable inputs/outputs for beam steering or directing. Other applications may have an array of antennas, only one of which is coupled to receiver/transmitter at a time. FIG. 1 illustrates a cascading switch array for coupling one of inputs I1-I4 to an output O1. The cascading switch array is made out of switches, e.g., PIN diode switches, S1-S7. To connect one of inputs I1-I4 to output O1, each of the switches S1-S7 assumes either a closed (short) or open position. For example, to connect input I1 to the output, switches S1, S5, and S7 assume the closed position, while the remaining switches assume the open position.
Antenna gain is an important characteristic of any transmission system. However, switches, such as PIN diode switches, have intrinsic insertion loss. For example, InGaAs/InP PIN diodes have been reported to have about 1.2 db insertion loss, while commercially available Agilent P940xA/C Solid State PIN diode switches are reported by the vendor to have 2.5 db insertion loss at 4 GHz. As can be seen from FIG. 1, when using a cascading switch arrangement, the insertion loss is compounded by the need to have several switches in the path. The example of FIG. 1, is used to connect one of only four possible inputs to the output, and necessitates three switches to be present in the path, tripling the insertion loss of the system. The insertion loss becomes even more acute if more inputs are required.
Accordingly, there is a need in the art for a switch design that minimizes insertion loss. Additionally, there is a need in the art for a switch design in which the insertion loss is not dependent on the number of inputs.